Connecting radiators with PEX

amuller

I know this is far from a new subject, but am wondering what most recent experience has to say about this.  Frankly, I'm having trouble getting comfortable with with idea of plastic for this application, but it seems many are using it, so....



I'm looking at a job with about ten column rads and a 75 k output pin-section gas boiler.

The system is a 1920s gravity circulation setup but damaged by freezing.  I'm thinking of a manifold approach with home runs to each rad.  Probably thermostatic valves on the rads.



Does the coating on the "barrier" pex work well enough to prevent deterioration of this sort of system, or would the P-A-P be better?  Would water treatment be needed?



I don't want to get fancy with controls--and can't afford to--but would like to leave future options open.



Can anyone point me to examples of such a setup?



Thanks in advance.

Charlie from wmass

If done correctly

It will work fine. It would give the best control of heat. Just make sure most of the radiators are ok before doing the repipe or make sure the customer is willing to pay for replacement radiators. A variable speed pump would be sweet and outdoor reset could get the fuel bill way down even in your area.

Bob Bona_4

perfect

PAP. Regular pex will move, droop, and cause misery. Manifold system, TRV's. Grundfos Alpha. Outdoor reset.



That's a sweet set up.

bob eck

radiators with pex pipe

Look at using Viega Fostapex pipe it is a full size pex tubing with aluminum for the oxygen barrier and the aluminum also keeps the pipe ridgid the pipe will not sag and it will not grow when running hot boiler water thru it. It is rated at 200* F @ 80n PSI / 180* F @ 100 PSI. I have a Triangle Tube PE110 condensing boiler installed on a old gravity system with cast iron radiators. This year I added three cast iron radiators on a second zone and I ran 1/2" Viega Fostapex out and back to each cast iron radiator. This pipe is great. So far I saw 150* F going out to the radiators and the fostapex pipe does not sag and does not grow.  

amuller

Thanks for the replies

I ordered a coil of PAP and some compression fittings, etc.  Any suggestions on manifolds to use?  Most of the radiant manifolds seem pretty expensive for this application, and common copper pex crimp manifolds won't work with APA.



Thanks.

Ironman

Manifolds

Don't try to get around using a good manifold - you'll regret it afterward. The manifold is one of the most important components and is necessary for proper filling, purging, balancing, etc. It wold cost 3 times more in materials and labor to piece meal something together that wouldn't work as well.



Many good ones out there. I've gotten used to Rehau Pro-Balance. You'll have to order your pipe connectors separately.  R -20 x P-A-P size.

Big Ed_4

reverse return

Just remember the first loop on the supply would be the last to return ...And if your using TRV's as control you must use a pressure release by pass so the circulator will not dead end...A outdoor reset would also be a plus

Leo_G

I still feel antsy

about using pex with alu after the Kitec debacle. So I just use straight oxy pex and support it well, giving it a bit of room to grow. With outdoor reset, I find the noises are kept to a minimum, and the addition of a good pressure sensing circ ( I like the grundfos brand) seems to keep the flow noise issue at bay also.



Oh yeah, the pex that I use is not layered, another to my mind, issue waiting to happen....